1. Field of the Disclosure
This disclosure relates in general to an image forming apparatus, such as a printer, and more particularly, to an image forming apparatus employing multiple black developer housings to improve monochromatic image quality.
2. Description of Related Art
Generally, the process of electrostatographic printing includes charging a photoreceptor member to a substantially uniform potential to sensitize the surface thereof. The charged portion of the photoreceptor surface is exposed to a light image from either a scanning laser beam, and LED source, or an original document being produced. This records an electrostatic latent image on the photoreceptor surface. After the electrostatic latent image is recorded on the photoreceptor surface, the latent image is developed. Two-component and single-component developer materials are commonly used for development. A typical two-component developer comprises magnetic carrier granules having toner particles adhering triboelectrically thereto. A single-component developer material typically comprises toner particles. Toner particles are attracted to the latent image, forming a toner powder image on the photoreceptor surface. The toner powder image is subsequently transferred to a copy sheet. Finally, the toner powder image is heated to permanently fuse it to the copy sheet in image configuration.
Image quality in printers has improved in the past by the introduction of hybrid scavengeless development (HSD) as shown, for example, in U.S. Pat. No. 6,668,146 B2. HSD technology develops toner via a conventional magnetic brush onto the surface of a donor roll. A plurality of electrode wires is closely spaced from the toned donor roll in the development zone. An AC voltage is applied to the electrode wires to generate a toner cloud in the development zone. This donor roll generally consists of a conductive core covered with thin (50-200 microns) partially conductive layer. The magnetic brush roll is held at an electrical potential difference relative to the donor roll to produce the field necessary for toner to adhere to the donor roll. The toner layer on the donor roll is then disturbed by electric fields from a wire or set of wires to produce and sustain an agitated cloud of toner particles. Typical AC voltages of the wires relative to the donor are 700-900 Vpp at frequencies of 5-15 kHz. These AC signals are often square waves, rather than pure sinusoidal waves. Toner from the cloud is then developed onto the nearby photoreceptor by fields created by a latent image.
However, even with the advent of hybrid scavengeless development, a problem remains as to how to compete with image quality of offset printing.